The specific objectives of this project are to determine the redistribution of ions which occur following coronary occlusion and to attempt to quantitate these changes in tissue which has been prepared by cryoultramicrotomy. Specimens will be analyzed in a Scanning Transmission Electron Microscope (STEM) with an Energy Dispersive Spectrometer (EDS). Elemental analysis will be performed in several intracellular organelles at various times after permanent and temporary coronary occlusion. The results will be compared with the ultrastructural appearance of the cells. Tissue processed for routine transmission electron microscopic analysis will also be examined with EDS to attempt to quantitate the extent of calciumphosphate binding which occurs. Agents known to influence calcium metabolism (verapamil and RO 2-2985) will be studied with these techniques to determine their effects on calcium accumulation in specific organelles. In selected cases Lanthanum nitrate or Diaminobenzidine Tetrachloride (DAB) will be infused to determine the extent of sarcolemmal disruption which is presented and this will be correlated with the data derived from EDS. It is anticipated that more precise and quantitative or semi-quantitative evaluation of ion alterations will be derived from this study which may be of value in the development of specific therapeutic agents for treatment of myocardial infarction.